Lighting systems may include light emitting devices organized in various configurations depending on the illumination applications. The LEDs are semiconductor devices that have a forward voltage. Different LEDs may have different forward voltages which may further vary based on operation of the LED. As LEDs heat up, the forward voltage drops and the current passing through the LED increases. For a given temperature, a small change in forward voltage can product a disproportionally large change in forward current. Also, the forward voltage required to achieve a desired light output can vary with LED die size, die materials, lot variations and temperature. In a circuit with LEDs and without regulation, the current will increase with an increase in supply voltage and/or a decrease in LED forward voltage, and, conversely, will decrease with a decrease in supply voltage and/or an increase in LED forward voltage.